1. Field of the Invention
This invention relates to a pump; and more particularly, relates to a centrifugal pump.
2. Description of Related Art
It is known in the art that if, e.g., a centrifugal pump, is turned on prior to being submerged air can become trapped inside of the housings containing the impellers causing them to pump a gas/liquid mixture instead of the pure liquid mixture they were designed to pump. When this occurs the pump tends to fail to pump water and the air must be expelled or pushed out of the system before the pump can operate as intended. When the pump fails, this situation is known as air lock.
FIG. 1 shows an air locked pump that is known in the art having a motor and an impeller for pumping an air/water mixture. With air inside the impeller housing, the impellers cannot create enough pressure to overcome the back pressure from the outlet hose. As shown, the pressure from the impellers is overcome by the back pressure from the outlet hose, so there is no flow out the outlet hose.
There are known devices whose purpose and intention is to prevent such air lock in, e.g., centrifugal pumps.
By way of example, U.S. Pat. No. 5,545,012, entitled, “Soft Star Pump Control System” discloses a technique, having a system that detects the presence of air lock by measuring the current through the pump motor at any given time. Should the pump detect air lock it uses a switching circuit to the lower the motor voltage and slowly ramp it up from a low value to its full value. However, the system in U.S. Pat. No. 5,545,012 does not always clear the air lock and is more complex than the system proposed in this document. The system also relies on the amount of current going through the motor which can vary greatly depending on the degree of air lock that a centrifugal pump is experiencing or the amount of charge left on a battery powering the system.
U.S. Pat. No. 4,087,994 entitled, “Centrifugal pump with means for precluding airlock” discloses another technique, having a pump with an impeller that contains finger-like protrusions designed to mix the trapped air with the water in the pump so it can be centrifuged out with the water.
U.S. Pat. No. 4,913,620, entitled “Centrifugal water pump,” discloses yet another technique, which consists of a pump whose impeller housing chamber has two walls. One of these walls has a radius close to the size of the impeller used in the pump and the other has a larger radius. There are also two terminal walls which direct the water flow to the outlet and break up any air and fills in any space where it could collect.
However, the techniques in U.S. Pat. Nos. 4,087,994 and 4,913,620 are both unnecessarily complex and because of this are cost prohibitive in many situations.
In view of this there is a need for a new, better and more cost effective way to prevent air lock, e.g., in centrifugal pumps.